F14 109 AO LS research proposal

Background

In the past few decades, there have been many advances in the field of plant engineering. Transgenic methods and genome editing have allowed for the improvement of drought resistance, crop yield, and pest resistance in various plants. Arguably the most successful genetic alteration conferring pest resistance is the insertion of cry genes from Bacillus thuringiensis (Bt) into crops. Bt was initially used for pesticidal sprays but the cry genes, which encode Cry proteins poisonous to a variety of insects, were isolated and transformed into crops by the mid 1990s. Despite the global success of Bt crops, there are still some concerns surrounding their use and their toxicity to humans, animals, and non-target pests alike. There was also a cross-fertilization scare in Mexico - later resolved - that reflected society and scientists' continued fear over a potential decline in biodiversity due to genetically modified organisms. Only MON 810 (Bt corn) is approved for cultivation in Europe, largely because of these cross-fertilization and long-term toxicity fears.

Research Idea and Significance

Our goal is to express insect repelling properties (such as the Bt Cry toxin) in only the somatic cells of plants, leaving the germ line of the crops unaffected. This would prevent cross-fertilization as well as toxicity to humans - as we tend to eat the fruit of plants. It would also protect monarch butterflies and other non-target insects from the harmful affects of toxins contained in pollen. We plan to study rhubarb as an example of this effect, as its leaves contain toxic substances but its stalks are safe for consumption. We will use maize as our model organism for better comparison against pre-existing pest repelling crops (such as Bt maize). We look to determine the growth rate, crop yield and level of toxicity of our engineered maize, as well as its effects on target and non-target pests.

Possible Outcomes & Troubleshooting

Possible data generated

Considerations like feasibility, scalability, policy, etc.

If we are unable to express Bt in somatic cells? Could try new plant, could try different places in the somatic genes, could try to minimize expression level of Bt in germ cells while still maintaining the sufficient level of pesticide to repel pests.

References

1. Shelton AM, Zhao JZ, Roush RT. Economic, ecological, food safety, and social consequences of the deployment of Bt transgenic plants. Annu Rev Entomol 2002; 47:845-881.
   1. Summary: Shelton et al. discuss many perspectives on using transgenic plants that express the insecticidal proteins of bacteria Bacillus thuringiensis (Bt). Since 1987, Bt has been used to in millions of hectacres of genetically modified crops and suggests a large economic gain. Bt has been used in tobacco, corn, potatoes and cotton, among others, however in 2002 scientists were still not sure of all of the risks of growing Bt crops. Of considerable interest to Shelton et al. were risks such as food safety, emergence of resistant insect populations, influence on non-target organisms, ethics and trade issues. They concluded that the benefits seemed to outweigh the risks with the knowledge available at that time and acknowledged many avenues of regulation.
2. Marshall A. 13.3 million farmers cultivate GM crops. Nature Biotechnol 2009; 27: 221-221.
   1. Summary: Andrew Marshall (2009) described global trends in GM crops. In 8 information-dense figures, Marshall shows data on global transgenic crops broken down by area, country, transgenic trait, and approvals in the US and EU. Notable data include that of the transgenic crops planted in 25 countries in 2008, over 90% were in developing countries however the US had the largest area of transgenic crops at 62% of the worldwide total.
3. Yu L, Chen X, Wang Z, Wang S, Wang Y, Zhu Q, Li S, Xiang C (2013). Arabidopsis Enhanced Drought Tolerance1/HOMEODOMAINGLABROUS11 Confers Drought Tolerance in Transgenic Rice without Yield Penalty. Plant Physiol 162(3):1378-1391.
   1. Summary: With a decreasing global supply of water, creating drought resistant plants is of great interest to the worldwide agriculture production market. Yu et al. (2013) created a strain of rice that had enhanced drought tolerance by isolating DNA of interest (AtEDT1/HDG11) from other drought-resistant plants and transforming it into the rice species of interest (Oryza sativa). The scientists constructed transgenic rice plants that overexpressed AtEDT1/HDG11, identified these plants by sequencing, and characterized them by RT-PCR and southern blot analysis. They found that the new transgenic species had a more robust root system and used water more efficiently, while increasing the yield of rice.
4. Jogaiah S, Govind SR, Tran LSP (2013) Systems biology-based approaches toward understanding drought tolerance in food crops. Crit Rev Biotechnol. 33(1):23-29.
   1. Summary: Jogaiah et al. (2013) discuss signaling network maps that have been constructed using plants. These network maps may be used in the fields of functional genomics and systems biology to analyze food crops and work toward understanding how food crops react to different environmental conditions.
   2. Good background information for article (Jogiah et al, 2013): Umezawa T, Fujita M, Fuita Y, Yamaguchi-Shinozaki K, Shinozaki K. Engineering drought tolerance in plants: discovering and tailoring genes to unlock the future. Curr Opin Biotechnol 2006, 17:113-122.
5. Comia L. Genome Elimination: Translating Basic Research into a Future Tool for Plant Breeding. PLoS Biol 2014; 12(6): e1001876.
6. Puchta H, Fauser F. Synthetic nucleases for genome engineering in plants: prospects for a bright future. The Plant Journal 2013; 78(5):727-741.
7. Belhaj K, Chaparro-Garcia A, Kamoun S, Nekrasov B. Plant genome editing made easy: targeted mutagenesis in model and crop plants using the CRISPR/Cas system. Plant Methods 2013; 9: 39.
8. McCouch S, Baute GJ, Bradeen J, Bramel P, Bretting PK, Buckler E, Burke JM, Charest D, Cloutier S, Cole G, Dempewolf H, Dingkuhn M, Feuillet C, Gepts P, Grattapaglia D, Guarino L, Jackson S, Knapp S, Langridge P, Lawton-Rauh S, Lijua Q, Lusty C, Michael T, Myles S, Naito K, Nelson RL, Pontarollo R, Richards CM, Rieseberg L, Ross-Ibarra J, Rounsley S, Hamilton RS, Schurr U, Stein N, Tomooka N, van der Knaap E, van Tassel D, Toll J, Valls J, Varshney RK, Ward J, Waugh R, Wenzl P & Zamir D. Agriculture: Feeding the future. Nature 2013; 499: 23-24.